1. Field of the Invention
Aspects of the present invention relate to an apparatus and a method for revising a halftoned image, and an image forming apparatus using the same, and more particularly, to an apparatus and a method for revising a boundary area of a halftoned image, and an image forming apparatus using the same.
2. Description of the Related Art
There is an image forming apparatus that represents a binary-level image, according to output and non-output dots, and there is an imaging apparatus that represents a multi-level image. The binary-level image forming apparatus converts a multi-level representation of an image into binary-level image, which is referred to as halftoning.
Among a variety of halftoning methods, a screening halftoning method is widely applied, particularly in the area of image forming apparatuses. The screening halftoning operates by binarizing gray levels from 0 to 255, of pixels of interest, based on a comparison with a predetermined screen.
According to the dot construction of a screen, a screen is mainly categorized into an amplitude modulated (AM) screen and a frequency modulated (FM) screen. The AM or clustered screen outputs clusters of dots, and provides a relatively more stable output of dots than the FM screen. Accordingly, the AM screen is generally used in image forming apparatuses.
In designing an AM screen, an initial location of a dot center is determined, and dots are grown, centered around the initial location. Therefore, the location of the dot center determines the lines-per-inch (LPI) of the resulting final screen table.
Halftoning generally softens images and details. However, halftoning using an AM screen does not represent details at a boundary area as clearly as using an FM screen.